I have found the later M8s to be quite reliable, once zero’ed. Dialing scopes they are not. I am very fond of both the 6x36 and 6x42. I have had a lot of both of these, never had one fail.

If accurate adjustments are important, as well as extreme reliability, I go with the now discontinued Nightforce NXS 2.5-10x32. I have four of these scopes, FWIW.